SOGI-FLL Based Advanced Adaptive Control of a PV-BES System for Weak Grid Operation

This paper presents a weak grid operation of a utility-integrated Photovoltaic (PV) - battery energy storage (BES) system delivering a non-linear load at the distribution end. The weak grid operational capabilities of the PV-BES system are ensured by second-order generalized integrated (SOGI) - fixed frequency loop (FLL) assisted constrained generalized maximum correntropy criteria (CGMCC) based adaptive control. The SOGI algorithm filters the grid voltage harmonics, subdues the effect of grid voltage sag/swell and unbalancing, and produces distortion-free and sinusoidal unit templates during weak grid conditions (WGC). FLL delivers the desired reference frequency to the voltage source converter (VSC) control algorithm. Likewise, CGMCC overcomes the current-related power quality issues arising from the non-linear load, i.e., current harmonics suppression, load balancing, active power control, and reactive power compensation at the point of common coupling (PCC). The FLL-SOGI complements the CGMCC algorithm in controlling VSC, keeping the PV-BES system stable, delivering PV power to the grid, and performing ancillary services. The BES system further enhances the DC bus stability by minimizing the effect of irregular PV power generation and reducing the DC bus voltage variations during diverse, dynamic conditions. The presented system's performance under numerous dynamic conditions and WGC is satisfactory per IEEE 1547–2019 standard.